Yogurt-cheese products, and methods of making the same

ABSTRACT

Techniques for making a yogurt-cheese-oil product, comprising steps of: providing a milkfat-oil fluid comprising butterfat and an oil; pasteurizing the milkfat-oil fluid to produce a cheese-oil precursor; combining yogurt with the cheese-oil precursor to produce a combined yogurt-cheese-oil precursor; and homogenizing and acidifying the combined yogurt-cheese-oil precursor; producing a yogurt-cheese-oil product. Yogurt-cheese-oil products: comprising between about 10% by weight and about 80% by weight of total butterfat; comprising between about 2% by weight and about 52.5% by weight of an oil; comprising between about 10% by weight and about 50% by weight of yogurt; and yielding less than about 1% syneresis by weight after 15 hours at about 74° F. to about 75° F.

This application is a continuation in part of commonly owned U.S. patentapplication Ser. No. 10/369,163, filed on Feb. 19, 2003; and acontinuation in part of commonly owned Patent Cooperation TreatyApplication Serial No. PCT/US2004/002538, filed on Jan. 29, 2004; and acontinuation in part of commonly owned U.S. patent application Ser. No.11/006,918, filed on Dec. 8, 2004.

FIELD OF THE INVENTION

The present invention relates to the field of cheese products andmethods for making the same. More particularly, the present inventionrelates to yogurt-cheese products that comprise yogurt and retain wheyfrom milkfat fluid used to make the products. These yogurt-cheeseproducts combine the desirable texture and mouth feel of cheese, havinga dramatically improved flavor due to retained whey, with theadditionally desirable taste and active culture bacteria health benefitsof yogurt.

BACKGROUND OF THE INVENTION

Cream cheese and similar products are ubiquitous in modern diets. Theygenerally have a smooth texture and a bland, unremarkable flavor.Spreadability makes cream cheese convenient to use, which is the primarybasis for its choice by consumers over other firmer cheeses and thereason for its high volume consumption as a topping, for example onbreads including bagels. In the classic method for making cream cheese,a pasteurized milkfat fluid such as cream, having a butterfat contentgenerally within a range of between about 34.5% by weight and 52% byweight, is the primary raw material. This milkfat fluid is subjected tothorough digestion by lactic acid-producing bacteria, homogenized, andclotted by enzymes or direct acidification. The milkfat fluid is thustransformed into a solid phase referred to as the curd, and a liquidphase referred to as the whey. Most of the butterfat content of themilkfat fluid is retained in the curd; and significant protein content,having nutritional value and much of the desirable potential flavor,remains in the whey. The curd is then processed into the desired creamcheese product, and the whey is discarded, along with its flavor. As aresult, cream cheese typically has a bland, dull, virtually unnoticeabletaste. The retention of liquid whey in the curd is a problem in itself,as the liquid gradually leaks out of the curd in an unappealing andongoing separation that is called syneresis. In addition, large scalecream cheese production generates corresponding quantities of oftenunusable whey, which thus becomes a waste expense and environmentaldetraction unless some other use can be found for it. Syneresis cansimilarly be a problem in many other cheese products.

The minimum butterfat content for cream cheese is 33% by weight. It is apervasive goal in the human diet to consume less fat; and the relativelyhigh butterfat content of a typical cream cheese is not helpful inachieving this goal. Countless attempts have been made to make low-fatcream cheese products, but the resulting cheese products have failed dueto unacceptable taste and poor texture. High fat concentrations are alsoa problem in many other cheese products.

Yogurt, another highly prevalent milk-derived product, has an entirelydifferent consistency than cream cheese, as well as a fundamentallydifferent flavor. In illustration, yogurt is considered to be a food,whereas cream cheese is considered to be a condiment. For example,yogurt, unlike cream cheese, is not a popular topping for bread productssuch as bagels. On the other hand, yogurt has a robust, desirableflavor. Yogurt also is typically lower than cream cheese in butterfat,cholesterol and sodium, and higher in protein.

A health-conscious consumer might well make the simple observation thatnonfat yogurt has a robust, desirable flavor, find the concept ofcombining yogurt and cream cheese to be desirable, and thus attempt tocombine these products together. However, due to the disparateproperties of cream cheese and yogurt, including for example theirdiffering consistencies, water content, and food chemistries, thecombination of cream cheese and yogurt in mutually appreciableproportions only generates a runny mess. A consumer might then attemptto drain the liquid from the solid phase of the yogurt before combiningin the cream cheese, thereby discarding whey from the yogurt. Similarproblems can be expected where other types of cheeses are substitutedfor cream cheese, where an attempt to combine such cheeses with yogurtis made.

Producing a cream cheese having an appealing consistency and utility,for example as a spreadable topping, is not possible by mixing creamcheese and yogurt without also adulterating these ingredients either bydiscarding whey from the yogurt or cream cheese, or by addingsubstantial proportions of gums and processed milk byproducts such asmilk protein concentrate, whole milk protein, whey protein concentrate,casein, Baker's cheese, yogurt powder, and dry cottage cheese curd. Atthat point, the product is no longer cream cheese but a processed cheesespread, typically having inferior texture and nutritional value, and aflavor that is either bland or even mildly unpleasant. Efforts have alsobeen made to produce so-called low-fat cream cheese, but again theresulting product has offered a bland, unremarkable and potentiallyunpleasant flavor. Hence, despite the broad popularity of cream cheese,its use typically entails consumer acceptance of a minimum butterfatcontent of 33% by weight, along with high cholesterol and sodium, and abland, unremarkable taste.

In addition to cream cheese, many other currently-available cheese-likedairy products also lack the health benefits of yogurt. For example,butter products in the form of either spreads or bricks often have veryhigh milkfat concentrations. Further for example, margarine products,which are designed to substitute for butter, often have very high oilconcentrations. Neither of these product classes typically comprisessubstantial concentrations of protein.

Accordingly it would be highly desirable to provide a process for makingan improved cheese product from a milkfat fluid, having the consistencyof high-milkfat cheese but combining the desirable flavor andnutritional benefits of yogurt with the flavor of whey retained from themilkfat fluid, yielding a robust taste. The resulting yogurt-cheeseproduct would be a welcome substitute for its faintly-tasting high-fatprogenitors while simultaneously improving cheese production economicsand protecting the environment. Since the butterfat content of yogurt istypically within a range of between about 0% and about 3.25% by weight,and commonly less than about 0.5% by weight, the combination of yogurtinto a cheese product also would desirably yield a cheese product havinga lower overall butterfat content and a relatively higher proteincontent. Cholesterol accompanies butterfat, so that the cholesterolcontent of this product would also be reduced.

SUMMARY OF THE INVENTION

In one implementation, a process for making a yogurt-cheese-oil productis provided, comprising steps of: providing a milkfat-oil fluidcomprising butterfat and an oil; pasteurizing said milkfat-oil fluid toproduce a cheese-oil precursor; providing a yogurt, and combining saidyogurt with said cheese-oil precursor to produce a combinedyogurt-cheese-oil precursor; and homogenizing and acidifying saidcombined yogurt-cheese-oil precursor; producing a yogurt-cheese-oilproduct.

In another implementation, a yogurt-cheese-oil product is provided:comprising between about 10% by weight and about 80% by weight of totalbutterfat; comprising between about 2% by weight and about 52.5% byweight of an oil; comprising between about 10% by weight and about 50%by weight of yogurt; and yielding less than about 1% syneresis by weightafter 15 hours at about 74° F. to about 75° F.

A more complete understanding of the present invention, as well as otherfeatures and advantages of the present invention, will be apparent fromthe following detailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart of an exemplary process for making ayogurt-cheese-oil product according to the present invention;

FIG. 2 is a flow chart of an exemplary process for making yogurt forincorporation as an ingredient in the process according to FIG. 1; and

FIG. 3 is a flow chart of an exemplary process for making a whippedyogurt-cheese-oil product.

DETAILED DESCRIPTION

Referring to FIG. 1, a flow chart of an exemplary process 100 is shownfor making a yogurt-cheese-oil product according to the presentinvention. According to this process, a cheese-oil precursor 105 isproduced in phase I generally indicated at 110. Subsequent steps definedin phase II generally indicated at 115 result in production of ayogurt-cheese-oil product 120.

Phase 1 of process 100 begins with provision of a milkfat-oil fluidcomprising an oil at step 125. By milkfat is meant a compositioncomprising the fatty components of edible milk, for example, cow milk.Such fatty components, commonly referred to collectively as butterfat,can include, for example, triacylglycerols, diglycerides,monoacylglycerols, and other lipids. By fluid is meant a liquefiedcomposition comprising milkfat, which can either be directly derivedfrom milk, or reconstituted by hydrating a dehydrated milk product. Forexample, the milkfat fluid can be cream. The milkfat fluid can be formedfrom a mixture of sources, including, for example, whole milk, cream,skim milk, and dry milk.

By oil is meant an edible oil of vegetable and/or animal origin. In oneembodiment, a vegetable oil is employed, such as, for example, avegetable oil derived from seeds or fruit of one or more of thefollowing: soy, corn, canola, sunflower, safflower, olive, peanut,cottonseed, sesame, almond, apricot, avocado, coconut, flax, grapeseed,hazelnut, palm, pine, poppy, pumpkin, rice bran, tea, walnut, and wheat.In another embodiment, an animal oil is employed, such as, for example,an animal oil comprising one or more of the following: lard, shortening,suet, and tallow. In one embodiment, the milkfat-oil fluid comprises aconcentration of a vegetable oil (weight/weight as a fraction of themilkfat-oil fluid) within a range of between about 3% and about 70%; andthe yogurt-cheese-oil product comprises a concentration of a vegetableoil (weight/weight as a fraction of the yogurt-cheese-oil product)within a range of between about 2% and about 52.5%. In anotherembodiment, the milkfat-oil fluid comprises a weight/weightconcentration of a vegetable oil within a range of between about 3% andabout 40%; and the yogurt-cheese-oil product comprises a weight/weightconcentration of a vegetable oil within a range of between about 2% andabout 30%. In another embodiment, the milkfat-oil fluid comprises aweight/weight concentration of a vegetable oil within a range of betweenabout 5% and about 27%; and the yogurt-cheese-oil product comprises aweight/weight concentration of a vegetable oil within a range of betweenabout 4% and about 20%. In a further embodiment, the milkfat-oil fluidcomprises a weight/weight concentration of a vegetable oil within arange of between about 8% and about 11%; and the yogurt-cheese-oilproduct comprises a weight/weight concentration of a vegetable oilwithin a range of between about 6% and about 8%.

In one embodiment according to the present invention, the milkfat fluidhas a butterfat content within a range of between about 10% and about52% by weight. In a further embodiment according to the presentinvention, the milkfat fluid has a butterfat content within a range ofbetween about 34.5% and about 52% by weight. In another embodimentaccording to the present invention, the milkfat fluid has a butterfatcontent within a range of between about 33% and about 50% by weight. Ina further embodiment according to the present invention, the milkfatfluid has a butterfat content within a range of between about 39% andabout 50% by weight. In another embodiment according to the presentinvention, the milkfat fluid has a butterfat content within a range ofbetween about 40% and about 44% by weight. In yet another embodimentaccording to the present invention, the milkfat fluid has a butterfatcontent within a range of between about 17% and about 33% by weight.Although much of the ensuing discussion is addressed to embodimentsaccording to the present invention for preparation of ayogurt-cheese-oil product having a butterfat content within a range ofbetween about 33% and about 50% by weight, it will be understood thatthe teachings according to the present invention may be applied tomaking products having a butterfat content within any of the otherranges defined above. The term yogurt-cheese-oil product as used hereintherefore generally refers broadly to all of such products.

In an additional embodiment according to the present invention, themilkfat fluid has a water content within a range of between about 50%and about 60% by weight. For example, heavy cream may have a butterfatcontent of about 37% by weight, a protein content of about 2% by weight,and a water content of about 58% by weight, with the balance made up byother milk solids. Butterfat is an essential ingredient in cheese, asthe butterfat is coagulated together with proteins and other elementsinto a curd and further processed to produce the cheese. The term“cheese” is broadly defined for purposes of this disclosure as a milkfatfluid that has been at least partially digested by culture bacteria.

In a further embodiment according to the present invention, themilkfat-oil fluid is pasteurized at step 130. Prior to this step, themilkfat-oil fluid typically carries the wild bacteria load normallypresent in raw milk products. Pasteurization of the milkfat-oil fluid isrequired at some point in order to kill these undesirable bacteria, aswell as other undesired microbes, to the extent reasonably feasible.Furthermore, if the milkfat-oil fluid is to be subjected to culturebacteria in steps 140-145 or steps 175-180 discussed below,pasteurization needs to be completed in advance of those steps or thewild bacteria in the raw milkfat-oil fluid will typically digest andthereby spoil the product. Where a source of pre-pasteurized milkfatfluid is employed, further pasteurization at this point may beunnecessary.

Pasteurization causes irreversible heat-induced denaturation anddeactivation of bacteria. Effective pasteurization is a function of bothtime and temperature; pasteurization can be completed at highertemperatures in correspondingly shorter times. In one embodimentaccording to the present invention, pasteurization of the milkfat-oilfluid in step 130 is carried out in a vat process at a temperature ofabout 150° Fahrenheit (“F.”) for about 30 minutes; or about 165° F. forabout 15 minutes; or if a more strenuous process is desired, about 170°F. for about 30 minutes. Other effective time and temperature treatmentparameters are known; and substitution of high surface area contactmethods for the vat process can permit shorter effective treatmenttimes. High temperature short time pasteurization for example, in whichthe milkfat-oil fluid is pumped through an in-line tube within atemperature-controlled shell, can be used. Milkfat fluids havingrelatively high butterfat content generally require more heat exposurethan low butterfat fluids in order to obtain effective pasteurization.Further background information on pasteurization of milk is provided inthe Grade “A” Pasteurized Milk Ordinance published on May 15, 2002 bythe U.S. Food & Drug Administration, particularly at pages 62 and 63;the entirety of which is hereby incorporated herein by reference.

Agitation is preferably provided and initiated prior to the heatingprocess during pasteurization to facilitate even heating throughout themilkfat-oil fluid and to avoid localized overheating. The force appliedby the agitation should not be so strong as to substantially shear andthus degrade the proteins, butterfat, and oil in the milkfat-oil fluid.Desirably, pasteurization is carried out in a tank equipped with aheater and agitator. Any suitable vessel can be used, such as, forexample, a Groen kettle.

In an alternative embodiment, the oil is added to the milkfat fluid at alater point in the process shown in FIG. 1. This addition is desirablycompleted prior to initiation of homogenization in step 185, discussedbelow, to ensure that the resulting product has a uniform texture.

According to one embodiment of the present invention, the temperature ofthe milkfat-oil fluid is adjusted at step 135 to a bacteria culturetemperature. In another embodiment according to the present invention,the temperature of the milkfat-oil fluid is adjusted to within a rangeof between about 65° F. and about 92° F. In an additional embodimentaccording to the present invention, the temperature of the milkfat-oilfluid is adjusted to within a range of between about 70° F. and about85° F. In yet a further embodiment according to the present invention,the temperature of the milkfat-oil fluid is adjusted to about 82° F.

In one embodiment according to the present invention, culture bacteriaare added to the milkfat-oil fluid at step 140, and then cultured atstep 145. The purpose of these steps is to generate robustculture-induced flavor in the milkfat-oil fluid. Milk contains lactosesugars that can be digested by selected bacteria, producing lactic acid,glucose and galactose as metabolites. Hence, the culture bacteriagenerally are selected from among those that can digest lactose.Preferably, a strain of mesophilic bacteria suitable for culturingcheese is used. Such bacteria strains are typically chosen to producediacetyl flavor. Bacteria strains may require ongoing rotational use, toprevent background bacteriophage populations from becoming resistant toa particular strain of bacteria, which can result in shutdown of theculture process and contamination of the product in production. Forexample, the culture bacteria may be selected from varying combinationsof strains, preferably rotated on an ongoing basis, of (1) lacticacid-producing Lactococcus lactis subspecies lactis or subspeciescremoris; and (2) diacetyl flavor-producing Lactococcus lactissubspecies diacetylactis or Leuconostoc strains. Suitable bacteriastrains are commercially available under the trade name pHage Control™from Chr. Hansen, Bøge Allé 10-12, DK-2970 Hørsholm, Denmark. Grades 604and 608 are particularly effective. These particular bacteria strainblends can be used continuously without rotation, provided that propersanitation is maintained. Further suitable bacteria strains arecommercially available under the trade names Flay Direct™ and DG™Cultures from Degussa BioActives, 620 Progress Avenue, P.O. Box 1609,Waukesha, Wis. 53187-1609.

Once a culture bacteria strain or strain mixture is selected, an amountis added to a given batch of milkfat-oil fluid that is effective topropagate live cultures throughout the batch in a reasonable time at thechosen culture temperature. For example, 500 grams of bacteria may beeffective to inoculate up to 7,500 pounds of milkfat fluid using aninoculation proportion of about 0.015%. If desired, an inoculationproportion within the range of between about 0.013% and about 0.026%,for example, may be used. In general, greater proportional additions ofculture bacteria to a milkfat fluid batch will lead to somewhat reducedprocessing time, but at the expense of increased costs for the bacteria.

In one embodiment according to the present invention, the milkfat-oilfluid is agitated following the addition of the culture bacteria, sincethe culture bacteria are typically added in a small proportion comparedwith the milkfat-oil fluid, and hence desirably are dispersed so thatthey can act throughout the milkfat-oil fluid. Agitation can if desiredbegin prior to addition of the culture bacteria, and can if desired becontinued after dispersion of the culture bacteria. The shear forceapplied by the agitation should be sufficient to disperse the culturebacteria in a reasonable time, but not so strong as to substantiallyshear and thus degrade the culture bacteria or the proteins, butterfatand oil in the milkfat-oil fluid. In one embodiment according to thepresent invention, moderate agitation of the milkfat-oil fluidcontaining the culture bacteria is continued for between about 10minutes and about 25 minutes. In another embodiment according to thepresent invention, moderate agitation is continued for about 15 minutes.

In step 145, the bacteria, if added at step 140, are cultured in themilkfat-oil fluid. In one embodiment according to the present invention,the milkfat-oil fluid is held at a suitable temperature long enough forcultures of the selected bacteria to begin development, resulting in aslight thickening of the milkfat-oil fluid. The necessary duration ofsuch bacteria culturing depends on the level of bacteria activity, theselected culture temperature, the initial bacteria concentration, andthe composition of the milkfat-oil fluid. The bacteria digest lactosesugars in the milk. Higher culture temperatures and initial bacteriaconcentrations generally shorten the culture time needed. Thetemperature employed, however, must be within a range tolerable to thesurvival and growth of the selected culture bacteria. In one embodimentaccording to the present invention, the milkfat-oil fluid is culturedwith the selected bacteria for between about 60 minutes and about 90minutes. A bacteria culture step of such a limited duration generates amild thickening of the milkfat-oil fluid.

In one embodiment according to the present invention, the butterfatcontent of the milkfat-oil fluid is standardized at step 150 to adesired level. The butterfat content of the final yogurt-cheese-oilproduct can then be projected based on the proportion of yogurt to beused, and its butterfat content. For example, cream cheese is defined toinclude a minimum butterfat content of 33% by weight. Given the variablenature of raw milk, for example, standardization of the butterfatcontent in a given batch of milkfat-oil fluid may generally be desirablein furtherance of process stability and production of a uniform product.According to one embodiment of the present invention, the butterfatcontent of the milkfat-oil fluid is adjusted to within a range ofbetween about 33% and about 50% by weight. According to anotherembodiment of the present invention, the butterfat content of themilkfat-oil fluid is adjusted to within a range of between about 33% andabout 36% by weight. According to a further embodiment of the presentinvention, the butterfat content of the milkfat-oil fluid is adjusted towithin a range of between about 33% and about 34% by weight. Accordingto yet another embodiment of the present invention, the butterfatcontent of the milkfat-oil fluid is adjusted to about 34.5% by weight.According to a further embodiment of the present invention, thebutterfat content of the milkfat-oil fluid is adjusted to within a rangeof between about 17% and about 33% by weight. According to yet a furtherembodiment of the present invention, the butterfat content of themilkfat-oil fluid is adjusted to within a range of between about 10% andabout 17% by weight.

In general, the texture and mouth feel of cheese products improves withhigher butterfat content. Higher butterfat levels also provide bettertolerance of the milkfat-oil fluid to processing steps, such asagitation shear that can degrade protein and butterfat molecules.However, higher butterfat levels also lead to correspondingly higherbutterfat content in the finished cheese, which is undesirable from ahealth standpoint. This standardization can alternatively be carried outprior to culturing the bacteria at step 145, but this practice generallyis not preferred.

The initial butterfat level present in a given batch of milkfat fluidcan be measured, for example, using a standard Babcock test. Forbackground, see Baldwin, R. J., “The Babcock Test,” MichiganAgricultural College, Extension Division, Bulletin No. 2, ExtensionSeries, March 1916, pp. 1-11; the entirety of which is hereinincorporated by reference. Where the initial butterfat level present ina given batch of milkfat fluid is too high, adjustment can beaccomplished by adding a nonfat material such as skim milk. Addition ofwater is generally ineffective since the water content of the curddirectly affects the product texture, and the feasibility of addingwater alone to adjust the butterfat level in the final product isaccordingly limited. In one embodiment according to the presentinvention, the butterfat content of a batch of milkfat fluid isdownwardly adjusted by addition of an appropriate amount of nonfat drymilk together with adequate water to rehydrate the nonfat dry milk,which has the advantage of not contributing excess water to the batch.In the event that the initial butterfat level present in a given batchof milkfat fluid needs to be upwardly adjusted, this can be accomplishedby addition of a material containing a higher concentration ofbutterfat, such as, for example, cream. The inclusion of an oil in themilkfat-oil fluid also reduces the overall butterfat concentration ofthe yogurt-cheese-oil product.

According to further embodiments of the present invention, the relativemilkfat-oil fluid concentrations of butterfat, milkfat protein, oil, andwater are all controlled. As explained above, the butterfat content ofthe final yogurt-cheese-oil product is selected as desired. For example,cream cheese includes at least about 33% by weight of butterfat.Regarding protein, higher concentrations are generally desirable fornutritional considerations. Regarding oil, desirably a sufficientconcentration is included to substantially reduce the butterfatconcentration and cholesterol level in the yogurt-cheese-oil product.Water is a secondary ingredient that is necessary to a reasonable degreeto facilitate processing, as well as to provide a desirable texture inthe product. However, excessive water will not be retained in the curdand hence becomes a processing hindrance and expense, and a disposalissue. In one embodiment according to the present invention, themilkfat-oil fluid comprises: about 34.5% to about 52% butterfat, about8% to about 2% oil, about 3% to about 7% milk protein, and about 51.5%to about 36% water, with the balance constituted by other milk solids.

Referring to FIG. 1, a stabilizer is desirably added to the milkfat-oilfluid at step 155. Stabilizers thicken the milkfat-oil fluid by bindingwater, which may contribute to retention of whey in the milkfat-oilfluid during subsequent processing. Step 155 is preferably carried outafter completion of any bacteria culture in steps 135-145 and aftercompletion of any standardization of the butterfat level at step 150;but can be carried out if desired at an earlier stage in phase I asgenerally indicated at 110. Step 155 can also be carried out if desiredat a later stage in the process shown in FIG. 1. However, step 155 ispreferably completed prior to homogenization step 185 discussed furtherbelow, so that any lumpy texture in the product resulting fromstabilizer addition is corrected during homogenization.

The stabilizer may be selected from, for example, gums, salts,emulsifiers, and their mixtures. Suitable gums include, for example,locust bean gum, xanthan gum, guar gum, gum arabic, and carageenan.Suitable salts include, for example, sodium chloride and potassiumchloride. These salts can also be added in suitable concentrations, ifdesired, as flavoring for the yogurt-cheese-oil product. Suitableemulsifiers include, for example, sodium citrate, potassium citrate,mono-, di-, and tri-sodium phosphate, sodium aluminum phosphate, sodiumtripolyphosphate, sodium hexametaphosphate, dipotassium phosphate, andsodium acid pyrophosphate. In one embodiment according to the presentinvention, the stabilizer is K6B493, a milled, dry product that iscommercially available from CP Kelco US, Inc., 1313 North Market Street,Wilmington, Del. 19894-0001. In another embodiment according to thepresent invention, the stabilizer is a distilled glyceride produced bythe distillation of mono-glycerides produced from esterification betweena triglyceride with glycerol. Variations are obtained through the choiceof triglycerides and the concentration of monoglyceride. Suitabledistilled glycerides are available from Danisco USA Inc., under thetrade name, DIMODAN®. Gum arabic is commercially available from TIC GumsInc., Belcamp, Md. A stabilizer blend comprising xanthan gum, locustbean gum and guar gum is also commercially available from TIC Gums Inc.Gum-based stabilizers typically contain sodium, which should be takeninto account in order to avoid excessive sodium concentrations in thefinal yogurt-cheese-oil product. For this reason, use of salts asstabilizers is also not preferred. However, the incorporation of asignificant proportion of yogurt into the final product reduces theproportional sodium content, as yogurt typically has a low sodiumconcentration.

Preferably, an amount of a stabilizer effective to cause a moderatethickening of the milkfat-oil fluid is added. For example, a stabilizermay be added in an amount constituting between about 0.2% by weight toabout 0.5% by weight of the yogurt-cheese-oil product. In anotherembodiment, a stabilizer may be added in an amount constituting about0.45% by weight of the yogurt-cheese-oil product. As the butterfatcontent of the chosen milkfat-oil fluid is reduced, the proportion ofstabilizer used preferably is increased.

In one embodiment according to the present invention, bacteria culturestep 145 is terminated by initiating pasteurization at step 160 beforesubstantial thickening of the milkfat-oil fluid occurs. In general,pasteurization step 160 is carried out in the same manner as discussedabove in connection with step 130. Limiting bacteria culture step 145 toa mild thickening of the milkfat-oil fluid according to this embodimentof the present invention is a fundamental and major departure fromnormal production, for example, of cream cheese, in which bacteriaculture is typically permitted to run its course until the pH of themilkfat-oil fluid is reduced to within a range between about 5.0 andabout 4.1. In the case of such a mild bacteria culture step, there maybe very little change in the pH of the milkfat-oil fluid. In oneembodiment according to the present invention, the temperature of themilkfat-oil fluid is gradually raised during processing in phase I, sothat the temperature continues to rise after completion of bacteriaculture in step 145. Hence, pasteurization is initiated in due coursewhen the milkfat-oil fluid reaches an effective pasteurizationtemperature.

In an alternative embodiment according to the present invention, thebacteria added to the milkfat-oil fluid at step 140 may be cultured fora sufficient time to partially or substantially digest the milkfat-oilfluid, as limited by the attendant pH reduction. Lactic acid is formedas a byproduct of metabolism of lactose by the bacteria in step 145.Hence, the measured pH of the milkfat-oil fluid, which graduallydecreases with lactic acid buildup, is an indication of the progress ofthe bacteria culture. If it is desired, for example, to substantiallydigest the milkfat-oil fluid, then the bacteria culture step 145 may becontinued until the pH of the milkfat-oil fluid is within a range ofabout 5.0 to about 4.1, or within a range of about 4.6 to about 4.4, ateither of which points the bacteria activity becomes substantiallydormant.

In one embodiment according to the present invention, the resultingcheese-oil precursor 105 is then cooled at step 165 to a suitabletemperature for subsequent combination of the cheese-oil precursor withyogurt in step 170. Once the pasteurization of the milkfat-oil fluid iscompleted, it is generally desirable to promptly lower the temperatureof the resulting cheese-oil precursor 105 to a more moderate level inorder to reduce ongoing heat damage to the butterfat, oil and milkproteins. In addition, it may be desired to downwardly adjust thetemperature of the cheese-oil precursor 105 so as not to unduly shock orkill the beneficial bacteria present in the yogurt during combination ofthe yogurt with the cheese-oil precursor, as will be discussed furtherbelow in connection with step 170. The high temperatures necessary forpasteurization cannot then be maintained, because they will kill thebeneficial yogurt bacteria.

More broadly, the cheese-oil precursor 105 is desirably cooled to atemperature that will facilitate reaching an appropriate temperature forcarrying out phase II. In one embodiment according to the presentinvention, the cheese-oil precursor 105 is cooled to a temperaturewithin a range of between about 110° F. and about 128° F. In anotherembodiment according to the present invention, the cheese-oil precursor105 is cooled to a temperature within a range of between about 115° F.and about 128° F. In a further embodiment according to the presentinvention, the cheese-oil precursor 105 is cooled to a temperaturewithin a range of between about 120° F. and about 125° F. In anadditional embodiment according to the present invention, the cheese-oilprecursor 105 is cooled to a temperature of about 125° F. If,alternatively, the cheese-oil precursor 105 will be stored prior tofurther processing, then it is preferably cooled to a refrigerationtemperature such as, for example, a temperature within a range ofbetween about 34° F. and about 38° F.

The resulting cheese-oil precursor 105 is then ready for furtherprocessing to prepare the yogurt-cheese-oil product 120 according tophase II generally indicated at 115 in FIG. 1. This cheese-oil precursor105 is a uniform, fluid material containing the butterfat and whey fromthe milkfat fluid, and an oil. The cheese-oil precursor 105 ischaracterized by substantially reduced bacterial activity due to itspasteurization. The preparation of the cheese-oil precursor 105 does notrequire and preferably does not include homogenization or acidificationat any point in phase I generally indicated at 110, which are stepsnormally included in preparation, for example, of cream cheese, althoughthese steps can be undertaken if desired. Acidification in phase I, forexample, would cause the curd and whey to separate, defeating the goalof including the whey from the milkfat fluid in the finalyogurt-cheese-oil product. Homogenization, for example, is whollyunnecessary in phase I of the production of the yogurt-cheese-oilproduct. Homogenization at this point would subject the cheese-oilprecursor 105 to unnecessary processing that would needlessly increasethe processing time and costs, while not substantially contributing tothe quality of the final yogurt-cheese-oil product.

The cheese-oil precursor 105 produced according to the process of thepresent invention is not, for example, cream cheese. Substitution of,for example, cream cheese for the cheese-oil precursor 105 as aningredient in step 170 to be discussed below defeats the desirable goalof providing a cheese product having retained whey, because whey isseparated from the curd in conventional cream cheese production.Moreover, cream cheese and yogurt cannot be directly combined inmutually substantial proportions to yield a homogenous single-phaseproduct. Substitution of other conventional cheeses for the cheese-oilprecursor similarly defeats the desirable goal of providing a cheeseproduct having retained whey.

Although the process according to the present invention does not produceconventional cheese, nevertheless conventional cheese such as creamcheese can if desired be an ingredient in the yogurt-cheese-oil product.For example, conventional cream cheese can, if desired, be added to thecheese-oil precursor 105 in any desired proportion. As the proportion ofconventional cheese in the final yogurt-cheese-oil product increases,the benefits of the teachings according to the present invention areachieved to a correspondingly reduced degree.

Referring to FIG. 1, the cheese-oil precursor 105 and a source of yogurtare then combined at step 170 to produce a combined yogurt-cheese-oilprecursor. In general, any yogurt may be used. Yogurt is broadly definedas a milkfat fluid that is cultured by at least one bacteria strain thatis suitable for production of yogurt. In one embodiment according to thepresent invention, the yogurt comprises: about 0% to about 3.25%butterfat, about 3% to about 6% milk protein, and about 76% to about 88%water. In another embodiment according to the present invention, theyogurt comprises: about 0.5% to about 3.25% butterfat, about 3.47% toabout 5.25% milk protein, and about 76% to about 88% water. In yet afurther embodiment according to the present invention, the yogurtcomprises: about 0.5% to about 2.0% butterfat, about 5% milk protein,and about 85% water. In still another embodiment according to thepresent invention, the yogurt comprises about 0.16% butterfat, about5.12% milk protein, and about 76% water. In general, any of theforegoing yogurts will have a total solids content of at least about 8%by weight.

In one embodiment according to the present invention, suitable yogurt260 is prepared according to the exemplary process 200 shown in FIG. 2.Referring to FIG. 2, milk is provided at step 210. The milk employed toproduce the yogurt 260 can be, for example, whole milk, reduced fatmilk, or skim milk. Butterfat present in the milk facilitates processingbecause butterfat contributes to the feasibility of thickening the finalproduct to a desirable consistency. However, butterfat present in themilk used in producing the yogurt 260 also results in a higher butterfatconcentration in the final yogurt-cheese-oil product. In one embodimentaccording to the present invention, the milk employed to produce theyogurt 260 accordingly is skim milk. In another embodiment according tothe present invention, the butterfat content of the milk is less than 1%by weight. In any case, the selected milk can be directly sourced fromliquid milk such as cow milk, or it can be reconstituted from dry milk.

In a further embodiment according to the present invention, the solidslevel of the milk to be used in preparing the yogurt 260 is standardizedto within a range of between about 18% and about 22% by weight. Inanother embodiment according to the present invention, the solids levelof the milk is standardized to about 22% by weight. If the solids levelof the milk is substantially in excess of 22% by weight, the bacteriaculture used to produce the yogurt 260 may digest the milk too slowlyfor practical production of yogurt. However, if a particularly robustbacteria strain is used, or if the milk is inoculated with an extra highbacteria load, use of milk with higher solids content may be feasible.Alternatively, the solids level of the milk can be standardized towithin a range of between about 10% and about 12% by weight, as isemployed in conventional preparation of yogurt. However, such arelatively low solids level can hinder production of a finalyogurt-cheese-oil product having a desirably thick texture. The solidscontent of the milk provided at step 210 can be increased if desired byany process suitable to yield a condensed milk. Condensation processesthat do not involve heating the milk, such as ultrafiltration, arepreferred in order to reduce processing damage of the milk.

At step 220, the milk is pasteurized. Pasteurization should generally becarried out as earlier discussed, for example, at a temperature of atleast about 165° F. for at least about 15 minutes. In one embodimentaccording to the present invention, pasteurization of the milk iscarried out at a temperature of about 170° F. for about 30 minutes.Agitation should be provided to facilitate even heating of the milk andto avoid localized overheating.

At step 230, the milk is then cooled to a bacteria culture temperature.Once the pasteurization of the milk is completed, it is generallydesirable to promptly lower the temperature of the milk to a moremoderate level in order to reduce ongoing heat damage. In addition,bacteria will be cultured in the milk at steps 240-250, as will bediscussed further below. As pointed out above, the high temperaturesnecessary for pasteurization cannot persist when the culture bacteriaare added at step 240. In one embodiment according to the presentinvention, the milk is cooled at step 230 to a temperature within arange of between about 90° F. and about 115° F. In another embodimentaccording to the present invention, the milk is cooled at step 230 to atemperature within a range of between about 106° F. and about 110° F. Inyet a further embodiment according to the present invention, the milk iscooled at step 230 to a temperature of about 108° F.

At step 240, culture bacteria are added to the milk. Since yogurt 260 isthe desired product of the process in FIG. 2, bacteria strains that aresuitable for production of yogurt are used. For example, Lactobacillusdelbrueckii subspecies bulgaricus, Streptococcus thermophilus,Lactobacillus acidophilus, Bifidobacterium, and Lactobacillus paracaseisubspecies casei can be used. If available, other lactic acid-producingbacteria strains suitable for making yogurt can be used. Suitable yogurtculture bacteria strains are commercially available under the trade nameYo-Fast® from Chr. Hansen, Bøge Allé 10-12, DK-2970 Hørsholm, Denmark.In one embodiment according to the present invention, F-DVS YoFast®-10is used, which contains blended strains of Streptococcus thermophilus,Lactobacillus delbrueckii subspecies bulgaricus, Lactobacillusacidophilus, Bifidobacterium, and Lactobacillus paracasei subspeciescasei. In another embodiment according to the present invention, DVSYoFast®-2211 is used.

In a further embodiment according to the present invention, a yogurtculture comprising Lactobacillus acidophilus, Bifidobacterium, and L.casei is used. For example, Yo-Fast® 20 cultures comprise mixtures ofLactobacillus acidophilus, Bifidobacterium, and L. casei. Such yogurtcultures can develop a very mild flavor and have high texturingproperties, making possible the reduction or elimination of stabilizersand additives that may otherwise be needed for increasing the productthickness. These yogurt cultures require minimal post-acidification,resulting in longer product shelf life. Such yogurt cultures also lend adesirable mouth feel and creaminess to low-fat products.

Further suitable bacteria strains are commercially available under thetrade names Ultra-Gro® and Sbifidus® from Degussa BioActives, 620Progress Avenue, P.O. Box 1609, Waukesha, Wis. 53187-1609.

Once a culture bacteria strain is selected, an amount is added to themilk that is effective to propagate live cultures throughout a givenbatch of milk in a reasonable time at the chosen culture temperature. Ingeneral, greater proportional additions of culture bacteria to a milkbatch will reduce processing time, but at the expense of increased costsfor the bacteria.

In one embodiment according to the present invention, the milk isagitated following the addition of the culture bacteria, since theculture bacteria are typically added in a small proportion compared withthe milk, and desirably are dispersed so that they can act throughoutthe milk. Agitation can if desired begin prior to addition of theculture bacteria, and can if desired be continued after dispersion ofthe culture bacteria. The shear force applied by the agitation should besufficient to disperse the culture bacteria in a reasonable time, butnot so strong as to shear and thus degrade the culture bacteria or theproteins and butterfat in the milk. In one embodiment according to thepresent invention, moderate agitation of the milk containing the culturebacteria is continued for between about 10 minutes and about 25 minutes.In another embodiment according to the present invention, moderateagitation is continued for about 15 minutes.

In step 250, the bacteria added at step 240 are cultured in the milk.The milk is held at a suitable temperature for cultures of the selectedbacteria to develop for a sufficient time so that there is visible curdformation throughout the milk, resulting in a substantial thickening. Inone embodiment according to the present invention, the milk is held at atemperature within a range of between about 95° F. and about 112° F. Inanother embodiment according to the present invention, the milk is heldat a temperature within a range of between about 100° F. and about 110°F. In a further embodiment according to the present invention, the milkis held at a temperature within a range of between about 106° F. andabout 110° F. In an additional embodiment according to the presentinvention, the milk is held at a temperature of about 108° F. Thenecessary duration of the bacteria culturing depends on the level ofbacteria activity, the selected culture temperature, the initialbacteria concentration, and the composition of the milk. In oneembodiment according to the present invention, the milk is cultured withthe selected bacteria for between about 4 hours and about 6 hours. Inanother embodiment according to the present invention, the milk iscultured with the selected bacteria at a temperature of about 108° F.for about 6 hours.

Lactic acid is formed as a byproduct of metabolism of lactose by thebacteria in step 250. Hence, the measured pH of the milk, whichgradually decreases with lactic acid buildup, is an indication of theprogress of the bacteria culture. Further, when the pH of the milkreaches about 4.4, the level of bacterial activity begins to markedlydecrease. In one embodiment according to the present invention, thebacteria culture step 250 is continued until the pH of the milk iswithin a range of about 5.0 to about 4.1. In another embodimentaccording to the present invention, the bacteria culture step 250 iscontinued until the pH of the milk is within a range of about 4.6 toabout 4.4; and more preferably about 4.5.

When the bacteria culture step 250 is complete, the resulting product isyogurt 260 containing live bacteria cultures. Preferably, the yogurt hasa uniform consistency with a solids content of at least about 8%.

Returning to FIG. 1, phase II begins with combining the cheese-oilprecursor 105 and a yogurt source together at step 170 to yield acombined yogurt-cheese-oil precursor. Yogurt 260 and the cheese-oilprecursor 105 desirably are simultaneously prepared so that phase II ofFIG. 1 as generally indicated at 115 can then immediately be carriedout. In this manner, the active yogurt 260 is already at a suitabletemperature, as discussed above, for combination with the cheese-oilprecursor 105 at step 170; and the cheese-oil precursor 105 can becooled at step 165 to that same temperature or to another compatibletemperature.

Alternatively, if the yogurt 260 is prepared in advance of undertakingphase II of FIG. 1, then the yogurt desirably is cooled in the meantimeto a refrigeration temperature such as, for example, within a range ofbetween about 34° F. and about 38° F., to retard unwanted continuationof bacterial activity, and is then reheated. In one embodiment accordingto the present invention, the yogurt 260 is reheated to a temperaturewithin a range of between about 95° F. and about 112° F. In anotherembodiment according to the present invention, the yogurt 260 isreheated to a temperature within a range of between about 100° F. andabout 110° F. In a further embodiment according to the presentinvention, the yogurt 260 is reheated to a temperature within a range ofbetween about 106° F. and about 110° F. In an additional embodimentaccording to the present invention, the yogurt 260 is reheated to atemperature of about 108° F. However, the necessary heat cycling in suchreheating causes degradation of the yogurt, including precipitation ofthe curd and attendant syneresis, and including a reduction in the liveyogurt bacteria concentration. Accordingly, reheating desirably isavoided.

In one embodiment according to the present invention, the cheese-oilprecursor 105 and yogurt 260 are combined together at step 170 of FIG. 1at selected temperatures, in selected proportions, and in a selectedmanner.

Ambient air contains harmful bacteria that can degrade the cheese-oilprecursor 105 and the yogurt 260. Accordingly, exposure of theseingredients during and after their preparation to air, as well as airexposure of the resulting combined yogurt-cheese-oil precursor and thecompleted yogurt-cheese-oil product, desirably are minimized.

Assuming that the above-discussed preparations of the cheese-oilprecursor 105 and yogurt 260 have been simultaneously completed, therespective temperatures of these ingredients are preferably controlledwith attention to preserving live culture bacteria in the yogurt, tominimizing further heating and cooling operations, and to preventingshock to or death of the live yogurt culture bacteria. Live yogurtbacteria cultures themselves provide well-known health benefits to theconsumer, and accordingly are preferably included in the finalyogurt-cheese-oil product. If either of the cheese-oil precursor 105 andyogurt 260 ingredients to be so used is either too hot or too cold, itstemperature can be adjusted. In one embodiment according to the presentinvention, the temperatures of the cheese-oil precursor 105 and theyogurt 260 are adjusted before combining them together to within a rangeof between about 110° F. and about 128° F., and to within a range ofbetween about 95° F. and about 112° F., respectively. In a furtherembodiment according to the present invention, the temperatures of thecheese-oil precursor 105 and the yogurt 260 are adjusted beforecombining them together to within a range of between about 115° F. andabout 128° F., and to within a range of between about 100° F. and about110° F., respectively. In another embodiment according to the presentinvention, the temperatures of the cheese-oil precursor 105 and theyogurt 260 are adjusted before combining them together to within a rangeof between about 120° F. and about 125° F., and to within a range ofbetween about 100° F. and about 108° F., respectively. In an additionalembodiment according to the present invention, the temperatures of thecheese-oil precursor 105 and the yogurt 260 are adjusted beforecombining them together to temperatures of about 125° F. and about 108°F., respectively.

The proportions of cheese-oil precursor 105 and yogurt 260 to becombined at step 170 are a matter of discretion. However, the cheese-oilprecursor 105 typically contains a relatively higher concentration ofbutterfat, and the yogurt 260 typically contains a relatively lowerconcentration of butterfat, cholesterol and sodium, and a relativelyhigher concentration of milk protein. Further, a substantialproportional addition of yogurt 260 to the cheese-oil precursor 105contributes the robust flavor, reduced cholesterol, and healthful activebacteria cultures of yogurt to the overall product. Hence, according toone embodiment of the present invention a sufficient proportion ofyogurt 260 is used relative to a given batch of cheese-oil precursor105, to yield a desired substantial improvement in the flavor and adesired substantial influence of the beneficial constituents in theyogurt on their mixture relative to that in the cheese-oil precursor.

According to another embodiment of the present invention, the mixture ofcheese-oil precursor 105 and yogurt 260 is controlled to comprisebetween about 10% and about 50% by weight of yogurt. In an additionalembodiment according to the present invention, the mixture of cheese-oilprecursor 105 and yogurt 260 is controlled to comprise between about 25%and about 40% by weight of yogurt. According to a further embodiment ofthe present invention, the mixture of cheese-oil precursor 105 andyogurt 260 is controlled to comprise between about 25% and about 35% byweight of yogurt. According to an additional embodiment of the presentinvention, the mixture of cheese-oil precursor 105 and yogurt 260 iscontrolled to comprise about 30% by weight of yogurt. Where flavoringsare to be added to the yogurt-cheese-oil product, slightly lowerproportions of yogurt generally are preferred, for example about 24% toabout 28% by weight of yogurt, and more preferably about 26% by weightof yogurt.

The cheese-oil precursor 105 and the yogurt 260 are combined together atstep 170. Desirably, this combination step is carried out within areasonable time following completion of the preparation of thecheese-oil precursor 105 in phase I shown in FIG. 1, and within areasonable time following completion of the preparation of the yogurt260 as shown in FIG. 2. However, provided that excessive bacterialactivity or heat-induced degradation is not permitted to take place ineither of these ingredients over an extended time period before they arecombined together, the cheese-oil precursor 105 and the yogurt 260 canbe separately stored as desired prior to carrying out step 170.

Where the relative proportion of yogurt 260 is small compared to theproportion of cheese-oil precursor 105, it is generally easier tocombine the minor yogurt ingredient into the major cheese-oil precursoringredient. In general, the cheese-oil precursor 105 and the yogurt 260are combined with moderate agitation for a time sufficient to thoroughlymix them together. Care should again be taken to minimize shearing ofmilk proteins, butterfat, oil, and the live culture bacteria. In oneembodiment according to the present invention, the combinedyogurt-cheese-oil precursor resulting from combination of the cheese-oilprecursor 105 and the yogurt 260 is then maintained at a temperaturewithin a range of between about 118° F. and about 125° F. In anotherembodiment according to the present invention, the combinedyogurt-cheese-oil precursor resulting from combination of the cheese-oilprecursor 105 and the yogurt 260 is then maintained at a temperaturewithin a range of between about 118° F. and about 120° F.

Desirably, the cheese-oil precursor 105 and yogurt 260 are thoroughlymixed before reaching homogenization at step 185 discussed below. Thismixing can be carried out in a vessel provided with an agitator,separate from the vessel in which the homogenization occurs. Suchthorough mixing prior to homogenization can result in a more uniformconsistency in the final yogurt-cheese-oil products. Such a vessel canbe provided with internal or external heating and cooling exchangers inorder to adjust or control the temperature of the combinedyogurt-cheese-oil precursor to a desired temperature as furtherdiscussed below. In one exemplary embodiment, this mixing is carried outfor a period of time within a range of between about 10 minutes andabout 30 minutes. In another exemplary embodiment, this mixing iscarried out for a period of about 15 minutes.

At step 185, the combined yogurt-cheese-oil precursor is homogenized bysubjecting it to an elevated pressure, desirably at an elevatedtemperature, for a suitable period of time. Application of such anelevated pressure breaks down the butterfat globules in the combinedyogurt-cheese-oil precursor, resulting in substantially increasedproduct uniformity. In general, homogenization is carried out at anelevated pressure, which can be applied to the combinedyogurt-cheese-oil precursor by any suitable means, such as, for example,hydraulic or mechanical force. In one embodiment according to thepresent invention, the combined yogurt-cheese-oil precursor iscompressed to the selected pressure and then passed through an orificeto quickly reduce such pressure. Homogenization is desirably carried outat a relatively high temperature, because the resulting fluidity of thecombined yogurt-cheese-oil precursor increases the efficiency of thehomogenization step. However, at a temperature greater than about 128°F. the desirable yogurt bacteria generally cannot survive, andtemperatures above about 125° F. result in gradual bacteria death.Accordingly, in one embodiment according to the present invention, thehomogenization step 185 is carried out at a controlled temperature notin excess of about 125° F. In another embodiment according to thepresent invention, homogenization is carried out at a controlledtemperature within a range of between about 118° F. and about 125° F. Ina further embodiment according to the present invention, homogenizationis carried out at a controlled temperature within a range of betweenabout 118° F. and about 120° F. Although higher temperatures can beused, desirably a temperature is chosen that will not kill the liveculture bacteria in the product. Homogenization can be carried out, forexample, in a Gaulin homogenizer.

In one embodiment according to the present invention, the homogenizationpressure is within a range of between about 2,000 pounds per square inch(PSI) to about 4,000 PSI. In another embodiment according to the presentinvention, the homogenization pressure is within a range of betweenabout 2,500 PSI to about 3,200 PSI. As the applied pressure increases,the resulting thickness of the final yogurt-cheese-oil productaccordingly increases. Hence, the pressure to be applied is preferablychosen to yield a final product of the desired consistency.

In one embodiment according to the present invention, a homogenizer isemployed having a homogenization chamber, an inlet chamber, and anoutlet chamber. The inlet chamber is a vessel suitable for staging asupply of the combined yogurt-cheese-oil precursor, on a continuous orbatch basis, for introduction into the homogenization chamber. Thehomogenization chamber is a vessel having controllable orifices forinput and output of the combined yogurt-cheese-oil precursor, and isreinforced to withstand containment of an elevated pressure suitable forhomogenization. The outlet chamber is a vessel suitable for staging asupply of the homogenized combined yogurt-cheese-oil precursor, on acontinuous or batch basis, for further processing. The combinedyogurt-cheese-oil precursor passes through the inlet chamber beforebeing pumped into the homogenization chamber. Following homogenization,the combined yogurt-cheese-oil precursor is expelled from thehomogenization chamber into the outlet chamber. These flows aretypically carried out on a continuous basis, although a batch processcan also be done. The pressure within the homogenization chamber isadjusted to the chosen homogenization pressure and maintained thereduring homogenization. The pressure in the inlet chamber may be, forexample, within a range of between about 20 PSI and about 40 PSI,generated by pumping of the combined yogurt-cheese-oil precursor intothe inlet chamber. Similarly, the pressure in the outlet chamber may be,for example, within a range of between about 20 PSI and about 40 PSI,generated by expelling the combined yogurt-cheese-oil precursor from thehomogenization chamber and then containing it in the outlet chamber. Thecombined yogurt-cheese-oil precursor can undergo a pressure drop uponpassing from the homogenization chamber to the outlet chamber, byejection through a hole, such as for example a hole having a diameter ofabout a centimeter. The pressures within the inlet chamber, outletchamber and homogenization chamber are carefully controlled so that airis not entrained into the homogenization chamber. Such air can causecavitation, which can degrade the product and potentially lead to anexplosive release of the homogenization pressure.

At step 190, the combined yogurt-cheese-oil precursor is acidified to apH suitable to retard activity of bacteria, and to complete thecoagulation of the combined yogurt-cheese-oil precursor to yield theyogurt-cheese-oil product 120. Desirably, acidification is carried outpromptly following formation of the combined yogurt-cheese-oil precursorat step 170. In one embodiment according to the present invention,acidification is completed within less than about three (3) hoursfollowing preparation of the combined yogurt-cheese-oil precursor atstep 170. In another embodiment according to the present invention,acidification is completed within less than about two (2) hoursfollowing preparation of the combined yogurt-cheese-oil precursor atstep 170. In a further embodiment according to the present invention,acidification is completed within less than about thirty (30) minutesfollowing preparation of the combined yogurt-cheese-oil precursor atstep 170. Where acidification is delayed substantially beyond threehours following preparation of the combined yogurt-cheese-oil precursorat step 170, the thickness of the final yogurt-cheese-oil product tendsto be correspondingly reduced, and the consistency of the product tendsto break down with attendant syneresis. While not wishing to be bound bytheory, it is believed that excessive bacterial activity in the combinedyogurt-cheese-oil precursor is a substantial contributing cause of theseadverse effects.

In one embodiment according to the present invention, a first point intime T1 when the cheese-oil precursor 105 and the yogurt 260 arecombined together at step 170 to produce the combined yogurt-cheese-oilprecursor, and a second point in time T2 when the combinedyogurt-cheese-oil precursor is acidified at step 190, are both monitoredand controlled. In a further embodiment according to the presentinvention, T2 is within about three (3) hours or less following T1. Inan additional embodiment according to the present invention, T2 iswithin about two (2) hours or less following T1. In another embodimentaccording to the present invention, T2 is within about thirty (30)minutes or less following T1.

In an additional embodiment according to the present invention, a firstpoint in time T1 when the cheese-oil precursor 105 and the yogurt 260are combined together at step 170 to produce a batch of the combinedyogurt-cheese-oil precursor, and a second point in time T2 when thebatch of combined yogurt-cheese-oil precursor is acidified at step 190,are both monitored and controlled. In a further embodiment according tothe present invention, T2 is within about three (3) hours or lessfollowing T1. In another embodiment according to the present invention,T2 is within about two (2) hours or less following T1. In an additionalembodiment according to the present invention, T2 is within about thirty(30) minutes or less following T1.

In the preceding embodiments wherein the first and second points in timeT1 and T2 are monitored and controlled, the time delay is managedbetween the point in time of production of a given portion of combinedyogurt-cheese-oil precursor and the point in time of acidification ofthat same portion. By “monitored” is meant that the first and secondpoints in time T1 and T2 are registered in a suitable manner, which mayfor example be automated or manual. By “controlled” is meant that thetime delay between the first and second points in time T1 and T2 isregulated in a suitable manner, which may for example be automated ormanual. In this manner, the yogurt-cheese-oil product generated from aparticular portion of combined yogurt-cheese-oil precursor will have adesirable thickness and shelf life. In a continuous productionoperation, the yogurt-cheese-oil product output from the process shownin FIG. 1 will be of a consistently satisfactory quality, withoutpockets of thin consistency or of propensity to accelerated spoilage. Ina batch production operation, the entire batch will be of suchsatisfactory quality, rather than resulting in pockets of poor qualityproduct or in sub-batches of varying quality. For example, a large batchof combined yogurt-cheese-oil precursor which is further processed as aseries of sub-batches will not be acidified over a time delay period inexcess of about three hours, thus preventing the generation ofsub-batches of declining quality as the delay increases.

Although the cheese-oil precursor 105 is pasteurized at step 160, theyogurt 260 typically contains live bacteria cultures and becomes themother culture for the combined yogurt-cheese-oil precursor.Accordingly, it is expected that other measures for retarding thebacterial activity in the combined yogurt-cheese-oil precursor can becarried out alternatively to or in conjunction with timed acidification.In one embodiment according to the present invention, homogenization andacidification are carried out on a substantially simultaneous basis inorder to minimize the time to completion of these steps. The optimumtemperature zone for rapid bacterial growth is generally within a rangeof between about 75° F. and about 115° F. Accordingly, the combinedyogurt-cheese-oil precursor and the resulting yogurt-cheese-oil productare desirably exposed to temperatures within this range for as short atime period as reasonably possible in order to minimize undesirable andexcessive bacterial activity and spoilage in the product. Hence, in oneembodiment according to the present invention, the temperature of thecombined yogurt-cheese-oil precursor is rapidly reduced to retardbacterial activity at a time following completion of step 170, andsubsequent steps in the process for making the yogurt-cheese-oil productare then carried out at such a reduced temperature or temperatures inorder to minimize the cumulative bacterial activity on the combinedyogurt-cheese-oil precursor during the balance of phase II. In a furtherembodiment according to the present invention, such temperaturereduction is carried out at a time following completion of step 170, butthe temperature of the combined yogurt-cheese-oil precursor issubsequently raised to optimize homogenization in step 185 as discussedabove and then is reduced again to retard bacterial activity. Theseembodiments may permit the completion of acidification step 190 to bedelayed for up to about seven (7) hours following preparation of thecombined yogurt-cheese-oil precursor at step 170.

In one embodiment according to the present invention, acidification step190 is carried out in the outlet chamber of the homogenizer discussedabove, desirably adjacent to the homogenization chamber. In this manner,step 190 can be carried out as soon as homogenization in step 185 iscompleted, typically on a continuous basis. The outlet chamber cancomprise, for example, a set tank internally equipped with a scrapedsurface agitator to ensure rapid and thorough mixing of added acid withthe homogenized combined yogurt-cheese-oil precursor. Agitationdesirably is discontinued upon reaching the desired product pH, in orderto avoid excessive shearing and possible resulting breakdown of thetexture of the yogurt-cheese-oil product. Acidification can generally becarried out at the same temperature range or temperature employed forhomogenization. For example, acidification can be carried out at atemperature of about 125° F. If desired, acidification can be carriedout at a lower temperature than that employed in homogenization step185, although the thickness increases as the temperature is reduced, andfeasibility of mixing the acidification agent into the yogurt-cheese-oilproduct is also important. In one embodiment according to the presentinvention, the temperature of the combined yogurt-cheese-oil precursoris reduced at least to a temperature within a range of between about112° F. and about 114° F. during or after acidification in step 190. Inanother embodiment according to the present invention, the temperatureof the combined yogurt-cheese-oil precursor is reduced to a temperatureof less than about 100° F. during or after acidification in step 190. Ina further embodiment according to the present invention, the temperatureof the combined yogurt-cheese-oil precursor is reduced to a temperatureof less than about 75° F. at a point during or after acidification instep 190. Carrying out acidification becomes gradually more difficult asthe temperature of the combined yogurt-cheese-oil precursor is lowered,due to the steadily increasing thickness. Furthermore, acidification ata temperature below about 60° F. may result in a lumpy yogurt-cheese-oilproduct texture. Cooling can be effected, for example, using jacketedtanks containing a glycol refrigerant maintained at a desiredtemperature to withdraw heat from the combined yogurt-cheese-oilprecursor in the tank.

Acidification causes substantial thickening of the combinedyogurt-cheese-oil precursor, and may hinder homogenization ifacidification is carried out before homogenization. However, the orderof homogenization step 185 and acidification step 190 can be inverted sothat acidification is carried out first, if desired; or as discussedearlier these steps can be concurrently carried out. For example,acidification step 190 can be carried out in the inlet chamber of ahomogenizer, the inlet chamber being equipped with a scraped surfaceagitator, or can be carried out as part of combining the cheese-oilprecursor 105 and yogurt 260 in step 170.

In one embodiment according to the present invention, the pH of thecombined yogurt-cheese-oil precursor is adjusted to within a range ofabout 5.0 to about 4.1, more preferably about 4.6 to about 4.4, andstill more preferably about 4.5. In another embodiment according to thepresent invention, the pH of the combined yogurt-cheese-oil precursorfor producing a plain yogurt-cheese-oil product, meaning one that doesnot contain or contains minimal concentrations of fruits, vegetables,nuts, flavorings, condiments or other food additives, is adjusted towithin a range of between about 4.40 and about 4.50. In a furtherembodiment according to the present invention, the pH of the combinedyogurt-cheese-oil precursor for a flavored yogurt-cheese-oil product,meaning one that does contain a significant concentration of fruits,vegetables, nuts, flavorings, condiments or other food additives, isadjusted to within a range of between about 4.38 and about 4.48. At a pHof the combined yogurt-cheese-oil precursor lower than about 4.40 or4.38 for plain or flavored yogurt-cheese-oil products respectively, thetaste begins to become sharp, and at a pH of about 4.2 or lower isgenerally too tart. At a pH of the combined yogurt-cheese-oil precursorabove about 4.50 or 4.48 for plain or flavored yogurt-cheese-oilproducts respectively, the product thickness begins to undesirablydecline, potentially resulting in poor body or runniness.

In one embodiment according to the present invention, the pH adjustmentis carried out by adding an appropriate amount of an edible acid to thecombined yogurt-cheese-oil precursor. Edible acids include, for example,lactic acid, phosphoric acid, acetic acid, citric acid, and mixtures.For example, a suitable aqueous mixture of edible acids having a pHwithin a range of between about 0.08 and about 1.4 is available underthe trade name Stabilac® 12 Natural from the Sensient TechnologiesCorporation, 777 East Wisconsin Avenue, Milwaukee, Wis. 53202-5304.Similar edible acid mixtures are also available from DegussaCorporation, 379 Interpace Parkway, P.O. Box 677, Parsippany, N.J.07054-0677. In another embodiment according to the present invention,the edible acid is lactic acid, being a metabolite naturally produced bythe lactose-consuming bacteria that are used in producing the yogurt 260and the cheese-oil precursor 105.

Since the thickness of the resulting product increases as the pH isreduced, edible acid addition can be used to control the thickness ofthe final yogurt-cheese-oil product. Furthermore, bacteria present inthe final product become substantially dormant at a pH substantiallybelow about 4.38, hence acidification substantially slows down theirfurther propagation in the product, extending its shelf life. However,the desirable yogurt bacteria are not killed by this acidificationprocess, and thus can still provide the health benefits of active yogurtcultures to the consumer. The edible acid present in the finalyogurt-cheese-oil product also serves to provide a good-tasting bite tothe flavor. At a pH of less than about 4.2, the product not only becomestoo tart but may also start to soften, reducing the product thickness.

In an alternative embodiment, a coagulating enzyme can be substitutedfor or used in conjunction with direct acid addition. Coagulatingenzymes cause the casein protein in milk to form a gel. However, theaction of coagulating enzymes generally requires much more time tocompletion than direct acidification, meanwhile allowing far moreculture bacteria activity to occur and delaying the completion ofacidification. The enzyme coagulation process is also accompanied bysyneresis and the resulting loss of albumin protein from the gelledcurd. Hence, enzyme coagulation generally results in an inferior producthaving a reduced thickness and protein content. However, it may befeasible to reincorporate the whey into the combined yogurt-cheese-oilprecursor so long as the enzyme coagulation is carried out beforehomogenization. Enzymatic coagulation typically takes a long time, 12hours for example. In general, any suitable coagulating enzyme ofanimal-, plant-, microbe, or other origin can be used. In oneembodiment, the coagulant enzyme is chymosin, also referred to asrennin, which is the active component of rennet. Rennet is purified fromcalf stomachs. Chymosin breaks down casein protein to paracasein.Paracasein then combines with calcium to form calcium paracaseinate,which precipitates and starts formation of a solid mass. Milkfat andwater become incorporated into the mass, forming curds. One part rennincan coagulate about 10,000 to about 15,000 parts milkfat fluid.Alternatively, pepsin, which is purified from the stomachs of growncalves, heifers, or pigs, can be used.

In order to facilitate the time-controlled and rapid completion ofacidification in step 190, live bacteria culture desirably is notcarried out in the combined yogurt-cheese-oil precursor prior to suchacidification. Assuming that the cheese-oil precursor 105 and the yogurt260 have separately undergone live bacteria culture steps as discussedabove, further culture of live bacteria in the combinedyogurt-cheese-oil precursor generally provides only marginal furtherflavor improvement. Moreover, the significant additional processing timerequired in order to add and culture such bacteria in the combinedyogurt-cheese-oil precursor delays the completion of acidification step190 and cooling of the yogurt-cheese-oil product to a temperature ofbelow about 75° F., which delay can result in lower product thicknessand shorter product shelf life.

In alternative embodiments according to the present invention, liveculture bacteria may be added to the combined yogurt-cheese-oilprecursor in step 175, and then cultured in step 180. If the yogurt 260employed at step 170 contains live bacteria cultures, then addingfurther culture bacteria at step 175 may be completely unnecessary andstep 175 can thus be omitted. Alternatively, if the selected yogurt 260does not contain live bacteria cultures, then such cultures may, ifdesired, be added at step 175. In another embodiment according to thepresent invention in which the cheese-oil precursor 105 was notsubjected to culture of bacteria at step 145, culture by yogurt bacteriamay be carried out at this point. In general, culture bacteria can be soadded if desired following the guidelines discussed above regarding step240 of FIG. 2, preferably with agitation. Live yogurt bacteria culturesthemselves provide well-known health benefits to the consumer, andaccordingly are preferably included in the final yogurt-cheese-oilproduct. Although the combined yogurt-cheese-oil precursor can also oralternatively be cultured by cream cheese culture bacteria such as maybe employed at step 140, such cream cheese bacteria do not typicallyprovide the health benefits that are provided to the consumer by liveyogurt bacteria. In a further embodiment according to the presentinvention, culture bacteria are added to the cheese-oil precursor 105following pasteurization step 160.

In one embodiment according to the present invention, yogurt bacteriaare then cultured in the combined yogurt-cheese-oil precursor at step180. The combined yogurt-cheese-oil precursor is held at a suitabletemperature for cultures of the selected bacteria to develop for asufficient time so that there is visible curd formation throughout thecombined yogurt-cheese-oil precursor, resulting in a substantialthickening and a significant reduction in the pH. In one embodimentaccording to the present invention, the combined yogurt-cheese-oilprecursor is held at a temperature within a range of between about 110°F. and about 120° F. In another embodiment according to the presentinvention, the combined yogurt-cheese-oil precursor is held at atemperature of about 108° F. In an additional embodiment according tothe present invention, the combined yogurt-cheese-oil precursor iscultured with the selected bacteria for between about 4 hours and about6 hours. In another embodiment according to the present invention, thecombined yogurt-cheese-oil precursor is cultured with the selectedbacteria at a temperature of about 108° F. for about 6 hours. In yet afurther embodiment according to the present invention, the bacteriaculture step 180 is continued until the pH of the combinedyogurt-cheese-oil precursor is within a range of about 5.0 to about 4.1,more preferably about 4.6 to about 4.4, and still more preferably about4.5.

Returning to FIG. 1, following completion of acidification step 190 thetemperature of the finished yogurt-cheese-oil product is preferablyreduced to a suitable refrigeration temperature, such as, for example,about 34° F. to about 38° F.

If desired, a suitable preservative can be added to theyogurt-cheese-oil product to retard bacteria, yeast and mold growth. Forexample, potassium sorbate, sodium benzoate, sorbic acid, ascorbic acidor nisin can be added, preferably before acidification step 190 andconsequent thickening, to facilitate their dispersion in minorproportion throughout the yogurt-cheese-oil product. Nisin, for example,is a protein expressed by Lactococcus lactis. Further, if desired,flavorings, condiments and the like can be added. In one embodiment, abutter flavoring is added to the yogurt-cheese-oil product. Butterflavorings are commercially available from Spice Barn Inc., 499 VillagePark Drive, Powell, Ohio 43065; and from Kernel Pops of Minnesota, 3311West 166^(th) Street, Jordan, Minn. 55352, an affiliate of R.D. Hanson &Associates, Inc. In another embodiment, a suitable coloring is added tothe yogurt-cheese-oil product, such as a yellow coloring for example.Beta carotene is a suitable yellow coloring, giving theyogurt-cheese-oil product a buttery appearance. Adjuvants that arevulnerable to attack by the live bacteria are preferably added afterreducing the temperature of the yogurt-cheese-oil product below about75° F., and may need to be made resistant to such bacteria.

In one embodiment, live yogurt culture bacteria are added to theyogurt-cheese-oil product in step 195 following completion ofacidification in step 190 and provided that the temperature of theyogurt-cheese-oil product is low enough at and following such additionto avoid killing or unduly shocking the live culture bacteria. Step 195can be carried out in the same manner as discussed above in connectionwith step 175. Such live bacteria reinforce the health-related benefitsof live and active yogurt culture bacteria in the yogurt-cheese-oilproduct, as earlier discussed. The need for such live culture bacteriaaddition and the concentration of such bacteria to be added to a givenyogurt-cheese-oil product can be determined by carrying out a bacteriaactivity test. For example a Man, Rogosa and Sharpe (“MRS”) broth testcan be carried out.

The yogurt-cheese-oil product made according to the process of thepresent invention generally has the appearance, consistency, and textureof a cheese or butter product. For example, the texture may be similarto that of cream cheese, or of another soft cheese. Alternatively, forexample, the product texture may be similar to that of butter ormargarine, in brick or spread form. In addition, this product has therobust, desirable flavor of yogurt. Further, the product includesretained whey from the milkfat fluid, which dramatically amplifies theflavor of the product, giving it a greatly superior and robust taste.Retention of the whey in this manner adds natural flavor withoutsubjecting the product to large proportions of adulterating additives orheavy extra processing steps, and eliminates the pollution and economicloss resulting from whey separation in conventional cheese production.Further, the yogurt-cheese-oil product comprises an oil, which improvesthe product spreadability, and contributes to the product texture. Inaddition, the yogurt-cheese-oil product has reduced cholesterol andsodium.

In one embodiment in accordance with the present invention, theyogurt-cheese-oil product comprises between about 10% and about 80%butterfat. In another embodiment in accordance with the presentinvention, the yogurt-cheese-oil product comprises between about 34.5%and about 52% butterfat. In one embodiment in accordance with thepresent invention, the yogurt-cheese-oil product comprises between about33% and about 40% butterfat. In another embodiment in accordance withthe present invention, the yogurt-cheese-oil product comprises betweenabout 17% and about 33% butterfat. In a further embodiment in accordancewith the present invention, the yogurt-cheese-oil product comprisesbetween about 10% and about 17% butterfat.

Addition of significant proportions of yogurt tends to somewhat reducethe butterfat content of the overall yogurt-cheese-oil product. Thus, inone embodiment according to the present invention, the yogurt-cheese-oilproduct comprises between about 8% by weight and about 35% by weight ofbutterfat. In another embodiment according to the present invention, theyogurt-cheese-oil product comprises between about 10% by weight andabout 26% by weight of butterfat. In yet another embodiment according tothe present invention, the yogurt-cheese-oil product comprises betweenabout 23% by weight and about 26% by weight of butterfat. In yet afurther embodiment according to the present invention, theyogurt-cheese-oil product comprises between about 25% by weight andabout 26% by weight of butterfat. In yet another embodiment according tothe present invention, the yogurt-cheese-oil product further comprisesbetween about 2% by weight and about 14% by weight of milk protein, morepreferably between about 3% by weight and about 8% by weight of milkprotein, and still more preferably between about 4% by weight and about5% by weight of milk protein. In yet a further embodiment according tothe present invention, the yogurt-cheese-oil product comprises betweenabout 2% by weight and about 52.5% by weight of an oil, more preferablybetween about 2% by weight and about 30% by weight of an oil, still morepreferably between about 4% by weight and about 20% by weight of an oil,and yet more preferably between about 6% by weight and about 8% byweight of an oil. In another embodiment according to the presentinvention, the yogurt-cheese-oil product comprises between about 0.05%and about 0.09% by weight of cholesterol; between about 0.2% by weightand 0.4% by weight of sodium; and between about 58% by weight and 63% byweight of water.

In one embodiment according to the present invention, inulin is added tothe yogurt-cheese-oil product. Inulin is a polysaccharide that isnaturally found in many plants. Inulin has a mildly sweet taste and isfilling like starchy foods, but is not normally absorbed in humanmetabolism and therefore does not affect the sugar cycle. Inulin reducesthe body's need to produce insulin, helping to restore normal insulinlevels. In addition to being thus beneficial for diabetics, inulincontributes to the body of yogurt-cheese-oil products, making possiblethe incorporation of as much as between about 2% and about 4% moreyogurt into a given yogurt-cheese-oil product. Inulin also is aprebiotic that extends the viability of the yogurt bacteria in thedigestive tract of the consumer, so that their beneficial effects in thebody are increased. Inulin may, however, be implicated in foodallergies, and can potentially induce anaphylactic shock in some people.Other non-digestible oligosaccharides and oligosaccharides resistant tometabolism, collectively referred to herein as “digestion-resistantpolysaccharides”, such as lactulose and lactitol, can also be used. Inone exemplary embodiment, inulin is added to the milkfat-oil fluid priorto pasteurization in step 130 discussed above.

Various highly processed dairy derivatives have the potential for use inmodifying the flavor and texture of cream cheese products. Thesederivatives include, for example, milk protein concentrate, whole milkprotein, whey protein concentrate, casein, Baker's cheese, yogurt powderand dry cottage cheese curd. Milk protein concentrate, for example, isproduced by ultrafiltration of milk. Such materials could be added tothe yogurt-cheese-oil product made in accordance with the presentinvention, or introduced during preparation of the product. However,their use is not preferred, and can by practice according to the presentinvention be minimized. Furthermore, addition of such agents generallyis a poor substitute for the retention of whey from the milkfat fluidand the incorporation of yogurt, both such desirable results being asachieved in accordance with the present invention. In one embodimentaccording to the present invention, at least about 40% of the milkprotein in the yogurt-cheese-oil product is derived from the milkfatfluid and yogurt. In another embodiment according to the presentinvention, at least about 50% of the milk protein in theyogurt-cheese-oil product, and potentially in excess of 60% of the milkprotein in the yogurt-cheese-oil product, is derived from the milkfatfluid and yogurt. The balance of the protein may be derived, forexample, from added nonfat dry milk and stabilizer.

Syneresis leads to an unattractive and wasteful phase separation betweencurds and whey when milk is directly coagulated. In one embodimentaccording to the present invention, the yogurt-cheese-oil productexhibits substantially no syneresis, or less than about 1% syneresis byweight, after 15 hours at a temperature within a range of between about74° F. to about 75° F.

The texture and consistency of the yogurt-cheese-oil product made inaccordance with one embodiment of the present invention is the same asthat of ordinary cream cheese. In another embodiment according to thepresent invention, the yogurt-cheese-oil product has a consistencysimilar to that of brick butter.

In yet a further embodiment according to the present invention, theconsistency of the yogurt-cheese-oil product can be modified to yield awhipped, more easily spreadable product. Referring to FIG. 3, anexemplary process 300 for carrying out a whipping operation is shown.The process begins with providing a yogurt-cheese-oil product at step310, in accordance with the above teachings. At step 320, theyogurt-cheese-oil product is agitated in the presence of an inert gas atan elevated pressure. For example, the yogurt-cheese-oil product can bepassed through a confined space having an agitator, while beingsimultaneously subjected to an inert gas at an elevated pressure.

In one embodiment according to the present invention, the inert gas isprovided at an initial pressure within a range of between about 150 PSIand about 240 PSI. In another embodiment according to the presentinvention, the inert gas is provided at an initial pressure within arange of between about 220 PSI and about 240 PSI. In yet a furtherembodiment according to the present invention, the pressure of the inertgas is controlled throughout the agitator in order to expose theyogurt-cheese-oil product to a desired pressure for a defined time as ittravels through the agitator. In another embodiment according to thepresent invention, the inert gas is injected into the agitator at achosen initial pressure, which is then permitted to dissipate in theregion of the agitator. In one embodiment according to the presentinvention, the yogurt-cheese-oil product is exposed to a desiredpressure for between about 3 seconds and about 6 seconds. In anadditional embodiment according to the present invention, theyogurt-cheese-oil product is exposed to a desired pressure for betweenabout 4 seconds and about 5 seconds. Although any inert gas can be used,nitrogen is the typical and most practical choice. By “inert” is meant agas that does not cause or at least minimizes undesirable effects on theyogurt-cheese-oil product, its production, and the consumer.

Injection of a gas into the yogurt-cheese-oil product under highpressure is problematic due to the extreme density mismatch of the gasand the yogurt-cheese-oil product. The gas diffuses into theyogurt-cheese-oil product. Diffusion of the gas throughout the body ofyogurt-cheese-oil product is not instantaneous even with agitation,effectively requiring a gas delivery pressure above and beyond thatnecessary for equalizing the prevailing pressure within the body ofyogurt-cheese-oil product. This resistance to gas dispersion in thesemi-solid yogurt-cheese-oil product can be ameliorated by employing anin-line gas injection system providing controllable gas injectionpressure and preferably having a relatively large bore gas deliveryorifice. A mass flow controller such as, for example, a GFC-171S massflow controller commercially available from Aalborg Instruments &Controls, Inc., 20 Corporate Drive, Orangeburg, N.Y. 10962, can be used.

In one embodiment according to the present invention, the temperature ofthe yogurt-cheese-oil product is reduced at step 340, and so maintainedor further modified during step 320. For example, a scraped surface heatexchanger, such as a Waukesha Cherry-Burrell Thermutator® or Votator®,can be used to provide the needed agitation while simultaneouslycontrolling the temperature. In one embodiment according to the presentinvention, the temperature of the yogurt-cheese-oil product is reducedto a suitable inert gas injection temperature at step 340, and is thenso maintained or further reduced during step 320. This temperaturereduction at step 340 increases retention of the inert gas in theyogurt-cheese-oil product during subsequent step 320. In the absence ofsuch a temperature reduction before injection of the inert gas,excessive escape of the inert gas from the yogurt-cheese-oil productprior to or during step 320 may retard the desired whipping process andresult in a product having a less whipped texture than desired. In oneembodiment according to the present invention, the yogurt-cheese-oilproduct is cooled at step 340 to an inert gas injection temperaturewithin a range of between about 65° F. and about 68° F., and agitationin the presence of the inert gas at an elevated pressure is then carriedout at a temperature within a range of between about 58° F. and about62° F. within the agitator at step 320. Using higher temperaturescounteracts the effect of the pressurized gas in causing theyogurt-cheese-oil product to expand into whipped form and accordingly isto be avoided. If desired, however, the yogurt-cheese-oil product may ingeneral be cooled to a whipping temperature within a range of betweenabout 65° F. and about 90° F., and more preferably cooled at least toabout 80° F., at step 340. A temperature within a range of between about58° F. and about 70° F., more preferably about 68° F. or lower, may thenbe employed within the agitator at step 320. Either or both of steps 340and 320 can include multiple cooling steps that reduce theyogurt-cheese-oil product temperature in a staged, controlled manner.This cooling can be carried out, for example, with a smooth and gradualtemperature reduction or in discrete steps. In one embodiment accordingto the present invention, step 340 is carried out immediately followingcompletion of homogenization in step 185 or immediately followingcompletion of acidification in step 190. For example, step 340 can becarried out in the outlet chamber of a homogenizer.

The agitation within the scraped surface heat exchanger may becontrolled to a desired level in order to maintain the yogurt-cheese-oilproduct within the exchanger for an adequate time for the pressurizedinert gas to act on the product. The normal operating speed of theagitator in a Waukesha Cherry-Burrell Thermutator® or Votator® may needto be reduced, for example to within a range of between about 800 and1,000 revolutions per minute, in order to avoid excessive shear. Inorder to facilitate further reduction of the temperature of theyogurt-cheese-oil product in the course of passage through the scrapedsurface heat exchanger, such exchanger is equipped to withdraw heat fromthe product, which is then dissipated in a suitable manner. In oneembodiment according to the present invention, two scraped surface heatexchangers are operated in series so that the yogurt-cheese-oil productis successively passed through both exchangers, which jointly cool andapply pressurized inert gas to the yogurt-cheese-oil product. In anotherembodiment according to the present invention, a Terlotherm® verticalscraped surface heat exchanger is employed. Terlotherm® machinery iscommercially available from Terlet USA, 6981 North Park Drive, EastBldg., Suite 201, Pennsauken, N.J. 08109.

The resulting product indicated at 330 is a whipped yogurt-cheese-oilproduct. The texture and consistency of the yogurt-cheese-oil productmade in accordance with one embodiment of the present invention is thesame as that of ordinary cream cheese. The texture and consistency ofthe yogurt-cheese-oil product made in accordance with another embodimentof the present invention is the same as that of whipped butter.

Where it is desired to add solid adjuvants such as fruits, vegetables ornuts to the yogurt-cheese-oil product, they are preferably added afterthe whipping process is completed.

Example 1

A batch of 1,500 pounds of pre-pasteurized heavy cream having abutterfat content of 44% is pumped into a kettle equipped with a heaterand an agitator. Olive oil in an amount of 15.5 gallons (116 pounds) isadded to the heavy cream. Sodium chloride in an amount of 11.4 pounds isadded to the heavy cream. The cream is then heated with agitation to 85°F., whereupon 500 milligrams of pHage Control™ 604 cream cheese culturebacteria are added to the cream with agitation for 15 minutes. The creamis then maintained at 85° F. for 75 minutes. The butterfat content ofthe cream is then adjusted to 33% by weight by the addition withagitation of 195.8 pounds of nonfat dry milk and 180 pounds of water.After 15 minutes of agitation, 9.01 pounds of K6B493 stabilizer is addedto the cream with agitation to thicken the mixture. The cream is thenpasteurized by heating it with agitation to 165° F. and holding at thattemperature for 15 minutes. The temperature of the resulting cheese-oilprecursor is adjusted to 130° F. Approximately 29% by weight of theprotein content in this cheese-oil precursor is derived from the cream;the balance being derived from the nonfat dry milk and stabilizer.

Meanwhile, yogurt is separately and simultaneously prepared. A batch of312 pounds of condensed nonfat milk having a solids content of 33% byweight is provided. The solids content is adjusted to 20% by weight, byaddition of 187 pounds of water. The condensed milk is then pasteurizedby heating it with agitation to 165° F. and holding at that temperaturefor 15 minutes. The temperature of the condensed milk is then adjustedto 108° F., whereupon 250 milligrams of F-DVS YoFast®-10 yogurt culturebacteria are added to the condensed milk with agitation for 15 minutes.The condensed milk is then maintained at 108° F. for 6 hours. Theresulting yogurt is then ready for combination with the cheese-oilprecursor. Next, 470 pounds of the prepared yogurt is mixed into 1,880pounds of the cheese-oil precursor with agitation. The mixture is cooledto a temperature of 125° F., and then homogenized by subjecting themixture to a pressure of about 3,000 PSI at a temperature of 125° F. forabout 5 seconds. The homogenized mixture is then acidified to a pH ofabout 4.5 by addition of 25 pounds of Stabilac® 12 Natural acid.

The resulting yogurt-cheese-oil product comprises about 25.9% by weightof butterfat; about 5% of oil, about 4.54% by weight of milk protein;about 0.0813% by weight of cholesterol; about 0.211% by weight ofsodium; about 58.3% by weight of water; and about 41.7% by weight ofsolids. Concerning the protein content of this final product,approximately: 57% is derived from the nonfat dry milk together with thestabilizer; 23% is derived from the cream; and 20% is derived from theyogurt. The yogurt-cheese-oil product yields substantially no syneresisafter 15 hours at about 74° F. to about 75° F.

Example 2

A batch of 1,335 pounds of pre-pasteurized heavy cream having abutterfat content of 44% is pumped into a kettle equipped with a heaterand an agitator. Olive oil in an amount of 8.8 gallons is added to theheavy cream. Sodium chloride in an amount of 13.68 pounds is added tothe heavy cream. The cream is heated with agitation to 85° F., whereupon500 milligrams of pHage Control™ 604 cream cheese culture bacteria areadded to the cream with agitation for 15 minutes. The cream is thenmaintained at 85° F. for 75 minutes. The butterfat content of the creamis then adjusted to 23.5% by weight by the addition with agitation of244 pounds of nonfat dry milk and 765 pounds of water. After 15 minutesof agitation, 11.25 pounds of K6B493 stabilizer is added to the creamwith agitation to thicken the mixture. The cream is then pasteurized byheating it with agitation to 165° F. and holding at that temperature for15 minutes. The temperature of the resulting cheese-oil precursor isadjusted to 128° F. Approximately 54% by weight of the protein contentin this cheese-oil precursor is derived from the cream; the balancebeing derived from the nonfat dry milk and stabilizer.

Yogurt is separately and simultaneously prepared in the same manner asdescribed in Example 1. Next, 500 pounds of the prepared yogurt is mixedinto 2,421 pounds of the cheese-oil precursor with agitation. Themixture is cooled to a temperature of 125° F., and then homogenized bysubjecting the mixture to a pressure of about 3,000 PSI at a temperatureof 125° F. for about 5 seconds. The homogenized mixture is thenacidified to a pH of about 4.5 by addition of 25 pounds of Stabilac® 12Natural acid.

The resulting yogurt-cheese-oil product comprises about 18.74% by weightof butterfat; about 3% of oil; about 8.85% by weight of milk protein;about 0.0613% by weight of cholesterol; about 0.331% by weight ofsodium; about 49.77% by weight of water; and about 50.23% by weight ofsolids. Concerning the protein content of this final product,approximately: 40.2% is derived from the nonfat dry milk together withthe stabilizer; 47.1% is derived from the cream; and 12.7% is derivedfrom the yogurt. The yogurt-cheese-oil product yields less than about 1%syneresis by weight after 15 hours at about 74° F. to about 75° F.

While the present invention has been disclosed in a presently preferredcontext, it will be recognized that the present teachings may be adaptedto a variety of contexts consistent with this disclosure and the claimsthat follow. For example, the process shown in the figures and discussedabove can be adapted in the spirit of the many optional parametersdescribed, to yield a variety of yogurt-cheese-oil products having abroad range of milkfat and oil concentrations.

1. A process for making a yogurt-cheese-oil product comprising steps of:providing a milkfat-oil fluid comprising butterfat and an oil;pasteurizing said milkfat-oil fluid to produce a cheese-oil precursor;providing a yogurt, and combining said yogurt with said cheese-oilprecursor to produce a combined yogurt-cheese-oil precursor; andhomogenizing and acidifying said combined yogurt-cheese-oil precursor;producing a yogurt-cheese-oil product.
 2. The process of claim 1, inwhich said oil constitutes between about 3% and about 70% by weight ofsaid milkfat-oil fluid.
 3. The process of claim 1, in which said oilconstitutes between about 3% and about 40% by weight of said milkfat-oilfluid.
 4. The process of claim 1, in which said oil constitutes betweenabout 5% and about 27% by weight of said milkfat-oil fluid.
 5. Theprocess of claim 1, in which said oil comprises a vegetable oil derivedfrom seeds or fruit of a member of the group consisting of: soy, corn,canola, sunflower, safflower, olive, peanut, cottonseed, sesame, almond,apricot, avocado, coconut, flax, grapeseed, hazelnut, palm, pine, poppy,pumpkin, rice bran, tea, walnut, wheat, and mixtures.
 6. The process ofclaim 1 comprising the steps of adding culture bacteria to saidmilkfat-oil fluid; and pasteurizing said milkfat-oil fluid before saidculture bacteria substantially digest said milkfat-oil fluid.
 7. Theprocess of claim 1 comprising the steps of providing a stabilizer, andadding said stabilizer to said milkfat-oil fluid.
 8. The process ofclaim 1 in which said cheese-oil precursor comprises retained whey fromsaid milkfat-oil fluid.
 9. The process of claim 1 in which saidcheese-oil precursor is not homogenized.
 10. The process of claim 1, inwhich said yogurt comprises between about 10% by weight and about 50% byweight of said yogurt-cheese-oil product.
 11. The process of claim 1, inwhich said milkfat-oil fluid comprises by weight about 34.5% to about52% butterfat, about 8% to about 2% oil, about 3% to about 7% protein,and about 51.5% to about 36% water, with the balance constituted byother milk solids.
 12. The process of claim 1, in which saidyogurt-cheese-oil product comprises a non-digestible polysaccharide. 13.A yogurt-cheese-oil product made according to the process of claim 1.14. The yogurt-cheese-oil product of claim 13, having less than about 1%syneresis by weight after 15 hours at a temperature within a range ofbetween about 74° F. and about 75° F.
 15. The yogurt-cheese-oil productof claim 13, in which at least about 40% of the milk protein is derivedfrom said milkfat-oil fluid and said yogurt.
 16. A yogurt-cheese-oilproduct: comprising between about 10% by weight and about 80% by weightof total butterfat; comprising between about 2% by weight and about52.5% by weight of an oil; comprising between about 10% by weight andabout 50% by weight of yogurt; and yielding less than about 1% syneresisby weight after 15 hours at about 74° F. to about 75° F.
 17. The productof claim 16, in which said oil constitutes between about 3% and about70% by weight of said milkfat-oil fluid.
 18. The product of claim 16, inwhich said oil constitutes between about 3% and about 40% by weight ofsaid milkfat-oil fluid.
 19. The product of claim 16, in which said oilconstitutes between about 5% and about 27% by weight of said milkfat-oilfluid.
 20. The product of claim 16, in which said oil comprises avegetable oil derived from seeds or fruit of a member of the groupconsisting of: soy, corn, canola, sunflower, safflower, olive, peanut,cottonseed, sesame, almond, apricot, avocado, coconut, flax, grapeseed,hazelnut, palm, pine, poppy, pumpkin, rice bran, tea, walnut, wheat, andmixtures.